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United States Patent |
6,019,663
|
Angell
,   et al.
|
February 1, 2000
|
System for cleaning semiconductor device probe
Abstract
A system and method for cleaning probe pins on a probe card used in testing
a semiconductor device during fabrication thereof. A ceramic cleaning
wafer is utilized to clean the probe pins without having to remove the
probe card from a production line. The same apparatus used to test
production wafers also handles the cleaning wafer during a probe cleaning
cycle. During operation of the cleaning cycle, the cleaning wafer is
placed in a manual load tray, which inserts the cleaning wafer into a
prober machine. The cleaning wafer is transported by a robotic trolley to
a prealign stage area where the cleaning wafer is aligned and centered.
The cleaning wafer is then placed on a support device. The support device
and cleaning wafer are positioned under a pneumatic sensor and profiled to
determine wafer planarity. The support device and cleaning wafer are then
positioned underneath the probe pins on the probe card to be cleaned.
Thereafter, the z-axis distance between the probe pins and the surface of
the cleaning wafer is decreased such that the probe pins contact the
cleaning wafer, thereby removing debris from the probe pins. The cleaning
wafer is then removed from the support device when cleaning of the probe
pins has been completed.
Inventors:
|
Angell; Larry D. (Boise, ID);
Krivy; Andrew J. (Boise, ID)
|
Assignee:
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Micron Technology Inc (Boise, ID)
|
Appl. No.:
|
027018 |
Filed:
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February 20, 1998 |
Current U.S. Class: |
451/5; 451/8; 451/527; 451/548; 451/559 |
Intern'l Class: |
B24B 049/00 |
Field of Search: |
451/5,8,65,360,67,526,527,548,559
|
References Cited
U.S. Patent Documents
1208688 | Dec., 1916 | Stempl, Jr. | 451/526.
|
3186135 | Jun., 1965 | Crean | 451/526.
|
4893438 | Jan., 1990 | Fry et al. | 451/526.
|
Other References
SupraSurf ADS-995 Thin Film Substrates, Coors Ceramics Company, Electronics
Division, Golden, Colorado (1987).
|
Primary Examiner: Eley; Timothy V.
Attorney, Agent or Firm: Workman, Nydegger & Seeley
Claims
What is claimed and desired to be secured by United States Letters Patent
is:
1. A system for cleaning probes used in testing a semiconductor device
during fabrication thereof, the system comprising:
a probe device having a plurality of probe pins on one side thereof;
a cleaning wafer having an abrasive surface capable of removing unwanted
debris from the probe pins, the cleaning wafer capable of blocking
transmission of nonionizing electromagnetic radiation energy therethrough;
and
a structure for supporting and moving the cleaning wafer which enables
contact of the cleaning wafer with the probe pins to remove debris from
the probe pins.
2. The system of claim 1, wherein the cleaning wafer is made from a ceramic
material.
3. The system of claim 2, wherein the ceramic material is selected from the
is group consisting of alumina, silicon nitride, silicon carbide, and
mixtures thereof.
4. The system of claim 1, wherein the cleaning wafer blocks transmission of
infrared light radiation therethrough.
5. The system of claim 1, wherein the cleaning wafer has a notch formed in
an outer periphery thereof.
6. The system of claim 1, wherein the cleaning wafer has a substantially
circular shape.
7. The system of claim 1, wherein the cleaning wafer has a thickness in a
range from about 10 mil to about 50 mil.
8. The system of claim 1, wherein a portion of the surface of the cleaning
wafer is made of an electrically conductive material.
9. The system of claim 1, wherein the cleaning wafer has metal traces
deposited on a surface thereof.
10. The system of claim 9, wherein the metal traces are gold traces.
11. A system for cleaning probes used in testing a semiconductor device
during fabrication thereof, the system comprising:
a probe device having a plurality of probe pins on one side thereof;
a cleaning wafer having an abrasive surface capable of removing unwanted
debris from the probe pins, the cleaning wafer capable of blocking
transmission of nonionizing electromagnetic radiation therethrough;
a tray for loading the cleaning wafer into the system;
a prealign stage area that is capable of aligning and centering the
cleaning wafer;
a robotic trolley for transporting the cleaning wafer to various stages in
the system; and
a vertically movable support device for holding the cleaning wafer and
bringing the cleaning wafer into contact with the probe pins to remove
debris from the probe pins.
12. The system of claim 11, wherein the cleaning wafer is made from a
ceramic material.
13. The system of claim 12, wherein the ceramic material is selected from
the group consisting of alumina, silicon nitride, silicon carbide, and
mixtures thereof.
14. The system of claim 11, wherein the cleaning wafer blocks transmission
of infrared light radiation therethrough.
15. The system of claim 11, wherein the cleaning wafer has a notch formed
in an outer periphery thereof.
16. The system of claim 11, wherein the probe device includes a probe card
having the plurality of probe pins thereon.
17. The system of claim 11, wherein the prealign stage area includes a
charge-coupled device camera array with optical character recognition.
18. The system of claim 11, wherein the robotic trolley includes a robotic
arm.
19. The system of claim 16, wherein the support device includes a vacuum
chuck capable of holding the cleaning wafer in position under the probe
card.
20. The system of claim 19, wherein the vacuum chuck includes a chuck top
for supporting the cleaning wafer under the probe card, and a z-stage
section interposed between the chuck top and a forcer section.
21. The system of claim 11, wherein the system is a computer-controlled
automated system.
22. A system for cleaning probes used in testing a semiconductor device
during fabrication thereof, the system comprising:
a probe device having a plurality of probe pins on one side thereof;
a cleaning wafer:
composed of a ceramic material selected from the group consisting of
alumina, silicon nitride, silicon carbide, and mixtures thereof;
having an abrasive surface capable of removing unwanted debris from the
probe pins, and having gold traces deposited on a surface thereof; and
capable of blocking transmission of nonionizing electromagnetic radiation
energy therethrough; and
a structure for supporting and moving the cleaning wafer which enables
contact of the cleaning wafer with the probe pins to remove debris from
the probe pins.
23. The system of claim 22, wherein the cleaning wafer blocks transmission
of infrared light radiation therethrough.
24. The system of claim 22, wherein the cleaning wafer has a notch formed
in an outer periphery thereof.
25. The system of claim 22, wherein the cleaning wafer has a substantially
circular shape.
26. The system of claim 22, wherein the cleaning wafer has a thickness in a
range from about 10 mil to about 50 mil.
27. The system of claim 22, wherein a portion of the abrasive surface of
the cleaning wafer is made of an electrically conductive material.
28. The system of claim 27, wherein the cleaning wafer is made from a
ceramic material.
29. The system of claim 28, wherein the ceramic material is selected from
the group consisting of alumina, silicon nitride, silicon carbide, and
mixtures thereof.
30. The system of claim 28, wherein the cleaning wafer has a thickness in a
range from about 10 mil to about 50 mil.
31. The system of claim 28, wherein a portion of the surface of the
abrasive cleaning wafer is made of an electrically conductive material.
32. The system of claim 28, wherein the cleaning wafer has metal traces
deposited on a surface thereof.
33. The system of claim 32, wherein the metal traces are gold traces.
34. A system for cleaning probes used in testing a semiconductor device
during fabrication thereof, the system comprising:
a probe device having a plurality of probe pins on one side thereof;
a cleaning wafer:
having an abrasive surface capable of removing unwanted debris from the
probe pins, the cleaning wafer capable of blocking transmission of
nonionizing electromagnetic radiation energy including infrared light
radiation therethrough;
having a substantially circular shape; and
having a notch formed in an outer periphery thereof;
a structure for supporting and moving the cleaning wafer which enables
contact of the cleaning wafer with the probe pins to remove debris from
the probe pins.
35. A system for cleaning probes used in testing a semiconductor device
during fabrication thereof, the system comprising:
a probe device including a probe card having the plurality of probe pins
thereon;
a cleaning wafer:
composed of a ceramic material is selected from the group consisting of
alumina, silicon nitride, silicon carbide, and mixtures thereof; and
having an abrasive surface capable of removing unwanted debris from the
probe pins, the cleaning wafer capable of blocking transmission of
nonionizing electromagnetic radiation therethrough;
a tray for loading the cleaning wafer into the system;
a prealign stage area that is capable of aligning and centering the
cleaning wafer;
a robotic trolley for transporting the cleaning wafer to various stages in
the system; and
a vertically movable support device including a vacuum chuck for holding
the cleaning wafer in position under the probe card and bringing the
cleaning wafer into contact with the probe pins to remove debris from the
probe pins, said vacuum chuck including a chuck top for supporting the
cleaning wafer under the probe card, and a z-stage section interposed
between the chuck top and a forcer section.
36. The system of claim 35, wherein the cleaning wafer blocks transmission
of infrared light radiation therethrough.
37. The system of claim 35, wherein the cleaning wafer has a notch formed
in an outer periphery thereof.
38. The system of claim 35, wherein the prealign stage area includes a
charge-coupled device camera array with optical character recognition.
39. The system of claim 35, wherein the robotic trolley includes a robotic
arm.
40. The system of claim 35, wherein the system is a computer-controlled
automated system.
Description
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates generally to semiconductor device testing
during fabrication. More particularly, the present invention relates to a
system and method that employs a cleaning wafer for in-line cleaning of
probe pins on a probe card used in testing semiconductor devices during
fabrication.
2. The Relevant Technology
During fabrication of semiconductor devices from silicon wafers, a prober
machine is used to interface a semiconductor device to a tester machine
while still in wafer form prior to cutting the wafer into individual
chips. A typical prober machine includes a probe card having an array of
probe pins that contact bond pads on the semiconductor device during
testing. The bond pads on the semiconductor device are made from metallic
materials such as aluminum which can oxidize when exposed to air. Also,
organic material left over from certain fabrication processes can be
disposed on the bond pads. When probe pin tips repeatedly contact bond
pads on a silicon wafer, metal oxides such as aluminum oxides and other
materials on the bond pads can build-up on the probe pin tips, thereby
interfering with the function of the probe pins during testing operations.
Thus, it becomes necessary to periodically clean the probe pins on a probe
card.
In conventional cleaning operations, a probe maintenance station is
utilized in order to clean probe pins on a probe card used in testing
fabricated semiconductor devices. This requires the removal of the probe
card from the production line in order to clean the probe pins, resulting
in a certain amount of production downtime. The production downtime
includes the time to remove the probe card from the prober, and the time
to install and perform a complete new set up for a clean probe card. Also,
additional time is spent in taking the dirty probe card to a hardware
support facility, in cleaning/aligning, and documenting the probe card,
and in getting the cleaned probe card back to production personnel.
As manufacturing techniques have improved, it has become possible to probe
more semiconductor dies in parallel at one time, requiring increasingly
wider probe card arrays. This has resulted in ever increasing difficulty
and downtime in order to have the probe card arrays taken off-line, to
replace the probe card arrays, and then to bring the system back on-line,
as well as additional time to clean the removed probe card arrays and
bring the arrays back into service. While various ceramic burnishing
chucks have been used in the past to clean probe tips, such as separate
chucks with a piece of ceramic thereon for the probes to touch down on for
cleaning, such conventional burnishing chucks are too small for the wider
probe cards currently used.
Accordingly, there is a need for improved probe pin cleaning systems and
methods that overcome or avoid the above problems.
SUMMARY OF THE INVENTION
The present invention is directed to a system and method that employs a
cleaning wafer such as a ceramic wafer disc for in-line cleaning of probe
pins on a probe device such as a probe card in a prober machine used in
testing semiconductor devices during fabrication. The shape and thickness
of the cleaning wafer is similar to a silicon production wafer, allowing
the cleaning wafer to be inserted in place of the silicon production wafer
in order to perform a cleaning cycle for the probe pins without having to
remove the probe card from a production line. The cleaning wafer is used
to make contact with the probe pin tips and remove any buildup of oxides
or other undesired substances that tend to accumulate on the probe pin
tips. The same apparatus used to test production wafers also handles the
cleaning wafer during a probe cleaning cycle.
During operation of the cleaning cycle, the cleaning wafer is placed in a
manual load tray or auxiliary tray, which inserts the cleaning wafer into
a prober machine. The cleaning wafer is transported by a robotic trolley
to a prealign stage area where the cleaning wafer is aligned and centered.
The cleaning wafer is then placed on a support device. The support device
and cleaning wafer are positioned under a pneumatic sensor and profiled to
determine wafer planarity. The support device and cleaning wafer are then
positioned underneath the probe pins on the probe card to be cleaned.
Thereafter, the z-axis distance between the probe pins and the surface of
the cleaning wafer is decreased such that the probe pins contact the
cleaning wafer. The probe pins can be repeatedly contacted with the
cleaning wafer to remove unwanted debris from the probe pins. The cleaning
wafer is removed from the support device and prober machine when cleaning
of the probe pins has been completed.
The cleaning wafer preferably has a substantially circular shape and blocks
transmission of nonionizing electromagnetic radiation energy therethrough
such as infrared light energy. In one embodiment, the cleaning wafer has a
first abrasive surface made of a ceramic material capable of removing
unwanted debris from a probe tip, and a second opposing surface having an
opaque coating thereon capable of blocking transmission of infrared light
energy through the wafer. An outer periphery between the first and second
surfaces has a notch formed therein to allow proper alignment of the
cleaning wafer when loaded into the prober machine.
The present invention allows probe pins on a probe card to be effectively
cleaned while still installed in a prober machine, thereby eliminating the
need to remove the probe card, reinstall a clean probe card, and rerun a
complete new set-up for the clean probe card. This results in a reduction
in production downtime.
Other aspects and features of the present invention will become more fully
apparent from the following description and appended claims, or may be
learned by the practice of the invention as set forth hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to more fully understand the manner in which the above-recited and
other advantages and objects of the invention are obtained, a more
particular description of the invention briefly described above will be
rendered by reference to specific embodiments thereof which are
illustrated in the appended drawings. Understanding that these drawings
depict only typical embodiments of the invention and are not therefore to
be considered limiting of its scope, the invention will be described and
explained with additional specificity and detail through the use of the
accompanying drawings in which:
FIG. 1 is a schematic plan view of a prober system that can utilize the
cleaning wafer according to the invention to clean probe pins on a probe
card used in testing semiconductor devices during fabrication;
FIG. 2 is a side view of part of the prober system of FIG. 1, showing the
cleaning wafer in position to clean the probe pins on a probe card;
FIG. 3 is an enlarged sectional side view taken along line 3--3 of FIG. 2,
depicting in more detail the probe pins in position to be cleaned by the
cleaning wafer according to the invention;
FIG. 4A is a plan view of one embodiment of a cleaning wafer according to
the present invention that can be utilized in the system of FIG. 1; and
FIG. 4B is a plan view of another embodiment of a cleaning wafer according
to the present invention that can be utilized in the system of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a system and method that employs a
cleaning wafer such as a ceramic wafer disc for in-line cleaning of probe
pins on a probe device such as a probe card in a production prober machine
used in testing semiconductor devices during fabrication. Thus, the
cleaning wafer of the invention is used to clean probe pins on a probe
card while still in a production setting. The shape and thickness of the
cleaning wafer is similar to a silicon production wafer. This allows the
cleaning wafer to be inserted in place of a silicon production wafer in a
prober machine in order to perform a cleaning cycle. The cleaning wafer is
used to make contact with probe pin tips and remove any buildup of oxides
or other undesired substances that tend to accumulate on the probe pin
tips. By making several touchdowns on the ceramic wafer disc, the oxides
or other debris can be cleaned from the probe pin tips.
The cleaning wafer of the invention can be made of any abrasive material
that has a suitable grain size for cleaning the probe pins. The rough
surface on the wafer acts as an abrasive to clean off the probe pin tips.
The cleaning wafer can be made from a variety of commercially available
materials. Preferably, a ceramic material is used to make the cleaning
wafer, including materials such as alumina, silicon nitride, silicon
carbide, tungsten carbide, and mixtures thereof. One suitable ceramic
material is SupraSurf ADS-995 available from Coors Ceramics Company, of
Oakridge, Tenn. This ceramic material has a 5 microinch surface finish,
with an average grain size of up to 2.2 microns, and is made primarily of
alumina.
The cleaning wafer preferably has a circular shape in the form of a flat
disc. The cleaning wafer can be formed such that both surfaces of the
wafer are abrasive. In one embodiment, the cleaning wafer of the invention
is sized to have a diameter of about 8 inches (about 200 mm) and a
thickness of from about 10 mil to about 50 mil, and preferably from about
20 mil to about 40 mil. The cleaning wafer preferably has a planar surface
that deviates less than about 6 microinches.
In order for the cleaning wafer of the invention to be properly loaded in a
prober machine during production, it is necessary to prevent radiant
electromagnetic energy from traveling through the cleaning wafer. Thus, a
ceramic cleaning wafer according to the invention is preferably rendered
opaque in order to block transmission of nonionizing radiant
electromagnetic energy therethrough, particularly in the infrared (IR)
wavelengths. Otherwise, if the cleaning wafer is translucent, IR wafer
sensors in the prober machine read through the translucent characteristics
of the cleaning wafer and the cleaning wafer is not loaded. The cleaning
wafer can be rendered opaque such as by being painted a dark color, or can
be made opaque originally. For example, a high temperature brown or black
paint can be sprayed on the backside of a ceramic wafer disc. This
prevents IR wafer sensors from reading through the ceramic wafer disc, and
enables the ceramic wafer disc to be loaded as if it were a silicon
production wafer.
As discussed in more detail below, the cleaning wafer of the invention has
a notch in an outer periphery thereof which allows for proper alignment of
the cleaning wafer when loaded into a prober machine. For example, a
1/8".times.1/16" notch can be cut in an outer periphery of a ceramic wafer
disc. The notch is used as a reference to establish coordinates at
0.degree., 90.degree., 180.degree., and 270.degree. around the wafer disc
during alignment of the wafer disc. This allows for orientating the wafer
disc and determining that the wafer disc has been centered and properly
aligned.
Referring to FIG. 1, a schematic overhead view of a prober machine or
system 10 is depicted, which can use the cleaning wafer according to the
invention to clean probe pins on a probe card. The prober system 10 is
basically an automated wafer handler that is used to interface a
semiconductor wafer with a testing device by using the probe pins on the
probe card for the electrical connections. The prober system 10 is run by
software designed to accommodate a special cleaning cycle using the
cleaning wafer of the invention to remove oxides and other debris from the
probe pins.
The prober system 10 includes a load station 12 having a manual loading
tray with a drawer that pulls out, allowing a cleaning wafer disc 30 to be
placed thereon and inserted into prober system 10. The wafer disc 30 may
also be placed on an auxiliary tray located under an indexer 13. The
indexer 13 is used for cassette loading of wafer disc 30 automatically. A
prealign stage 14 in prober system 10 includes a charge-coupled device
(CCD) camera array 16, with optical character recognition (OCR). An
optical sensor in camera array 16 detects a notch in cleaning wafer disc
30 to properly align cleaning wafer disc 30 automatically. The cleaning
wafer disc 30 is profiled at load position 20 by a profiler device (not
shown), discussed in further detail below, to determine the thickness and
planarity of cleaning wafer disc 30. The prober system 10 also includes a
robotic trolley 18 having a robotic arm that is adapted to transport
cleaning wafer disc 30 to the various stages of prober system 10. For
example, robotic trolley 18 is utilized to move cleaning wafer disc 30
from the loading tray to prealign stage 14, and from prealign stage 14 to
a load position 20. The prober system 10 also includes a probe station 22.
As shown in FIGS. 2 and 3, a means for supporting cleaning wafer disc 30 in
the form of a support device 32 is provided in prober system 10. The
support device 32 can be a vacuum chuck used to hold cleaning wafer disc
30 in position under a probe card 24 with probe pins 26 at probe station
22. The cleaning wafer disc 30 is held such that an abrasive surface 42 of
wafer disc 30 faces probe pins 26 to be cleaned. The support device 32 has
a top portion 34 such as a chuck top which supports cleaning wafer disc
30, and a z-stage section 36, which is interposed between top portion 34
and a forcer section 38 that floats pneumatically against a platen 40. The
forcer section 38 moves z-stage section 36 and has the ability to
compensate for any unevenness of cleaning wafer disc 30 and variations in
surface height of cleaning wafer disc 30.
When wafer disc 30 is placed on the chuck top of support device 32, the
center of wafer disc 30 should align exactly with the center of the chuck
top. Due to various reasons, however, this alignment does not always occur
and the profiler device is employed to perform the alignment. The profiler
device hardware includes an electronics control module (ECM) and a
pneumatic sensor. The profiler device measures the wafer disc diameter and
finds the center of the wafer disc in relation to the center of the chuck
top. The profiler device then sends the exact wafer location information
to support device 32 so that proper adjustments are made. The profiler
device uses backside spindle contact to measure the profile, thickness,
and diameter of the wafer disc to automatically find the wafer center and
wafer edge. The measurements are taken at either 1, 3, 5, or 9 points on
the wafer.
The sensor of the profiler device may be lowered into operating position or
raised into a ring carrier under program control. The sensor emits a
stream of air which is used to detect back pressure, that is, how much air
is being reflected or bounced back into the sensor from a surface. This
detected back pressure is used to determine the thickness of the wafer
disc under the sensor. The detected back pressure is compared by the
electronics to a preset reference. The output of this comparator function
can be one of three states: sensor less than a reference, sensor equal to
a reference, or sensor greater than a reference. The comparator output is
sensed by the profiler software. For example, the ECM can be set up so
that the equal condition occurs when the wafer disc (or chuck top) is 10
mils below the sensor. This 10-mil distance is the reference distance,
which means the wafer disc is more than 10 mils from the sensor, exactly
10 mils from the sensor, or less than 10 mils from the sensor. To measure
wafer thickness, z-stage section 36 is raised up until the comparator
switches from the "wafer more than 10 mils from sensor" state into either
the "exactly 10 mils from sensor" state or the "less than 10 mils from
sensor" state.
FIG. 3 shows an enlarged side view of probe card 24 with probe pins 26
thereon which are positioned to be contacted with abrasive surface 42 of
cleaning wafer disc 30 supported on top portion 34. The probe card 24 can
have about 600 to 800 or more pins on a printed circuit board for probe
card 24. The probe pins 26 are preferably at about an 8.degree. angle
orientation from a horizontal plane.
FIG. 4A shows more detail of cleaning wafer disc 30 with abrasive surface
42, which can be used in prober system 10 to clean probe pins 26 on probe
card 24. The cleaning wafer disc 30 has a notch 31 along the outer
periphery thereof to provide for proper alignment of wafer disc 30 at
prealign stage 14 in prober system 10.
FIG. 4B depicts another embodiment of the cleaning wafer of the invention
in the form of a cleaning wafer disc 50, which can also be utilized in
prober system 10 to clean probe pins 26 on probe card 24. The cleaning
wafer disc 50 has a notch 51 along the outer periphery thereof to provide
for proper alignment of wafer disc 50 in prober system 10. The cleaning
wafer disc 50 has two distinct sections on the surface thereof that will
face the probe pins 26, including an abrasive section 52 which can be made
of a ceramic material, and a conductive section 54 made of an electrically
conductive material such as a metal. As discussed in more detail below,
conductive section 54 allows probe pins 26 to be tested during the
cleaning cycle without having to remove cleaning wafer disc 50 from prober
system 10.
In operating prober system 10 of FIG. 1 in order to run a cleaning cycle
for probe pins 26 on probe card 24, the various components of prober
system 10 utilized during testing of silicon production wafers are also
employed to align and load the cleaning wafer. Thus, cleaning wafer disc
30 is placed in the manual loading tray at load station 12 as indicated by
arrow A to begin a cleaning cycle for prober system 10. Alternatively, the
wafer disc 30 can be placed in an auxiliary tray from indexer 13. The
robotic trolley 18 picks up cleaning wafer disc 30 as indicated by arrow
B, and moves cleaning wafer disc 30 to prealign stage 14 as indicated by
arrow C, where cleaning wafer disc 30 is spun to locate the notch thereon.
The robot arm on robotic trolley 18 picks up cleaning wafer disc 30 and
slides wafer disc 30 over to where it is perfectly centered on prealign
stage 14, and wafer disc 30 is reoriented to have a start position of from
0.degree. to 360.degree. (e.g., 0.degree., 90.degree., 180.degree.,
270.degree.) from the notch thereon. The robot arm then moves wafer disc
30 to load position 20 as indicated by arrow D and onto top portion 34 of
support device 32, which in turn is moved to probe station 22 as indicated
by arrow E so that wafer disc 30 is underneath probe card 24. The vertical
or "z" height of support device 32 is then adjusted up and down as needed
to perform the cleaning operation. The cleaning wafer disc 30 is kept
stationary beneath probe card 24 during the cleaning cycle as probe pins
26 are touched down on wafer disc 30. The probe pins 26 can be repeatedly
contacted with cleaning wafer disc 30 as needed to remove unwanted debris
from probe pins 26. The cleaning wafer disc 30 is removed from support
device 32 and from the prober machine when cleaning of probe pins 26 has
been completed.
When the probe pins are contacted with the cleaning wafer of the invention,
a certain amount of over-travel or flexing of the pins occurs. For
example, after initial contact of the probe pins on the surface of the
cleaning wafer, the z height of the cleaning wafer can be further
increased so that the pins have about a 3 to 5 mil over-travel. There are
two options for moving the probe pins to produce a desired over-travel.
The first option is simply to move the probe pins up and down, which will
bend the probe pin tips up and down. The second option is to utilize a jog
mode in which the probe pins come down on the cleaning wafer, press down,
and then move up. In the jog mode, the probe pins are moved in the x
direction, the y direction, and then an x-y direction so that the probe
pins are being moved in a generally octagonal pattern in three-dimensions
while contacting the cleaning wafer. This allows the probe pin tips to be
cleaned all over.
The prober system 10 is configured to automatically load the cleaning wafer
to begin a cleaning cycle, perform some touch downs of the probe pin tips
on the cleaning wafer to remove debris from the probe pin tips, unload the
cleaning wafer, and resume testing of production wafers. Accordingly, a
prober control is employed capable of running an external routine that
will control prober system 10 so that the necessary commands required to
perform the cleaning cycle are executed. For example, a portable computer
can be operatively connected to prober system 10 to run a generic
communications program. Such a program can instruct prober system 10 to
profile a loaded cleaning wafer to determine the thickness and planarity
of the cleaning wafer so that any variations can be compensated for by
z-stage section 36 on support device 32. The program can also instruct
prober system 10 to move the cleaning wafer to a specific x-y location
that centers the chuck/wafer under the center of probe card 24, and then
z-up to the current z-work-height plus the entered z over-travel value.
The program can then tell prober system 10 to unload the cleaning wafer to
the manual loading tray or the auxiliary tray.
The prober system 10 can be configured to load the cleaning wafer after a
set number of probe pin touch downs on a production wafer, or the probe
pins can be randomly tested to see whether or not a cleaning cycle is
needed. Testing criteria can be built into production test programs so
that the resistivity of the probe pins is checked to determine if cleaning
is required. For example, resistance in the probe pins can be measured
such that if resistivity increases by more than 4 ohms in the probe pins,
an error signal is triggered and a cleaning cycle is commenced.
Alternatively, correlation failure tests can be run to check the probe pins
for debris build-up. For example, a whole production wafer can be run on
one system and then the production wafer can be run on another system. A
map overlay is then done to see bin failure swapping. If one site on the
tested probe card varies from any of the other sites by more than a
standard deviation, a site difference signal is triggered and production
will stop. The cleaning wafer of the invention can then be used to clean
the probe pins before production is continued.
The probe pins on the probe card can be electrically tested during the
cleaning operation to determine if the probe pins have been sufficiently
cleaned, such as by gauging the resistance of the probe pins. For example,
a production wafer can be shuttled back and forth to the probe card or a
production wafer can be placed near the probe card to provide a ground for
the probe pins so that the pins can be electrically tested to determine
whether the cleaning job is sufficient. A continuous cycle between the
production wafer and the cleaning wafer can be run until electrical
testing proves that the probe pins have been sufficiently cleaned, and
then regular production and testing of silicon wafers can be resumed.
In addition, as discussed above, the cleaning wafer can include a
conductive section on a surface thereof, allowing the probe pins to be
tested during the cleaning cycle without having to remove the cleaning
wafer away from the probe card. The conductive section can be used as an
electrical ground site for testing the probe pins to determine if the
cleaning has been sufficient. For example, the probe pins can be
alternately cleaned and tested during the cleaning cycle until it is
determined that the cleaning is satisfactory through various diagnostics.
Once the probe pins have been sufficiently cleaned, production can be
resumed by shuttling a production wafer into the prober machine.
Further, after a predetermined period of use, the cleaning wafer itself can
be cleaned of the oxides and other materials that have been scraped off
the probe pins, allowing the cleaning wafer to be repeatedly reused. In
another option, the life of the cleaning wafer or time between cleanings
of the wafer can be extended by simply using a different notch offset for
wafer orientation. The CCD in the prealign stage can be instructed,
through software, to look for the notch and rotate the cleaning wafer to a
different position so the same cleaning wafer is used for another set of
cleaning cycles. For example, there can be one setting at 0.degree., which
can be used for 100 cleaning cycles, another setting at 90.degree., which
can be used to enable another 100 cleaning cycles, a different setting at
180.degree., which can be used for another 100 cleaning cycles, and
another setting at 270.degree., which can be used to enable another 100
cleaning cycles. The different settings allow each set of 100 cleaning
cycles to be performed at different locations on the cleaning wafer,
thereby extending the life of the cleaning wafer.
In another embodiment, a plurality of metal traces such as gold traces can
be placed on the cleaning wafer. The metal traces can be placed on the
cleaning wafer by a conventional deposition process such as chemical vapor
deposition. The metal traces can serve as ground sites for electrically
testing the probe pins during a cleaning cycle, and can also be used to
provide a first-to-last contact planarity range for the probe pins. Since
the probe pins on a probe card are at various heights, by touching the
pins down on the metal traces, it can be determined incrementally at what
point individual probe pins contact the surface of the cleaning wafer.
The cleaning wafer embodiments of the invention can thus be used in
cleaning probe pin tips and to test whether the probe pin tips are
sufficiently clean, and can be used in determining the planarity of the
probe pins.
The cleaning wafer of the invention allows wider probe cards to be
effectively cleaned while still loaded on a production prober machine.
This allows the probe pins to be in service longer without having to
remove the probe card for cleaning, reinstall a clean probe card, and
rerun a complete new set-up for the clean probe card. Thus, the invention
results in a decrease in production downtime that is associated with the
removal of a known good probe card that just needs the probe pin tips
scrubbed or cleaned.
The present invention may be embodied in other specific forms without
departing from its spirit or essential characteristics. The described
embodiments are to be considered in all respects only as illustrative and
not restrictive. The scope of the invention is, therefore, indicated by
the appended claims rather than by the foregoing description. All changes
which come within the meaning and range of equivalency of the claims are
to be embraced within their scope.
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